Kettle Bell Training

I am thinking of adding a day or two of kettle bell training, as I've heard that it really helps built up the muscles and keeps you limbre and ready for a fight as it were. There is a good company here in Melbourne that stocks a kettlebell and dvd packs and looks quite good, but was wondering how anyone else here has done with kettlebells or kettlebell training in general.

I saw an ad for Joe Wieder's PowerBell or something like that, which is an adjustable weight kettle bell type thingy. It seemed intriguing. A friend of mine had an old school 35# which is an ass-kicker.

I had a personal trainer who liked to incorporate them into my workout. Great for core training if done with proper form (feet/ankles firmly on ground, knees bent, swing up to shoulder height and back down, thrusting hips forward on the swing up, core/abs tight and flexed during the movement). Just another good variation to mix up a core workout.